DESCRIPTION(adapted from applicant's abstract): Our visual systems are constantly confronted with environments rich in objects, of which only a few (at most) are relevant for our immediate goals. However, all of the objects in our environment, relevant or not, initiate visual processing through the stimulation of our retinae. Visual selective attention imparts a special processing status on those items deemed to be task relevant. The long term goals of this research program are to understand the mechanisms by which visual selective attention selects and augments the processing of those task-relevant objects. This project explores attentional selection mechanisms by examining the perceptual fate of unattended objects. Recent empirical studies have found that the processing of objects neighboring an attended object is inhibited relative to the processing of other, more distant objects. This finding suggests that the attentional selection of an object may occur in part through the inhibition of neighboring objects. The proposed research explores the mechanisms by which this occurs. Specifically, a model of attentional selection is proposed and evaluated. The model proposes that objects compete for shared, spatially dependent processing resources. When objects are near one another, they must compete for a set of shared resources. Objects high in attentional salience win this competition -- and hence a greater proportion of the processing resources--leading to the poorer perceptual performance for their lower salience neighbors. As the objects become more distant, they recruit from progressively more independent sets of resources. The experiments in this proposal are designed to evaluate various components and assumptions of this model.